KR102222499B1 - Organic light emitting display device - Google Patents

Abstract

The present invention relates to an organic light emitting display device. The organic light emitting diode display includes a first flexible substrate, a second flexible substrate facing the first flexible substrate, a plurality of organic light emitting pixels disposed between the first flexible substrate and the second flexible substrate and disposed on the first flexible substrate, An adhesive layer disposed between the 1 flexible substrate and the second flexible substrate, an encapsulation unit configured to protect a plurality of organic light emitting pixels from oxygen and moisture, and an adhesive layer disposed on the encapsulation unit to bond the first flexible substrate and the second flexible substrate together. Includes. A neutral surface is formed adjacent to the plurality of organic light emitting pixels, and the elastic modulus value of the adhesive layer has a value equal to or greater than a predetermined elastic modulus so as not to be deformed by bending stress when the first flexible substrate is stored in a roll form, The thickness of the adhesive layer is determined in consideration of the thickness of the first flexible substrate, the critical radius of curvature of the first flexible substrate, and the elastic modulus of the adhesive layer.

Description

Organic light emitting display device {ORGANIC LIGHT EMITTING DISPLAY DEVICE}

The present invention relates to an organic light-emitting display device, and more particularly, to an organic light-emitting display device having a structure capable of reducing deformation due to bending stress of a flexible organic light-emitting display device.

As the information age enters in earnest, the field of display devices for visually displaying electrical information signals is rapidly developing. Accordingly, research is being conducted to develop performances such as thinner, lighter, and low power consumption for various display devices. Typical examples of such flat panel display devices include liquid crystal display devices (LCD), plasma display panel devices (PDP), field emission display devices (FED), and electrowetting display devices. (electro-wetting display device: EWD) and organic light emitting display device (OLED).

In particular, the organic light-emitting display device is a self-luminous display device, and unlike a liquid crystal display device, it does not require a separate light source, and thus can be manufactured in a lightweight and thin form. In addition, the organic light emitting display device is not only advantageous in terms of power consumption, but also has excellent response speed, viewing angle, and contrast ratio, and thus is being studied as a next-generation display. However, despite these advantages, the organic light emitting display device is particularly vulnerable to moisture and oxygen, and thus it is difficult to secure reliability compared to other display devices.

The organic light-emitting display device includes an organic light-emitting device including an anode, an organic light-emitting layer, and a cathode. Here, the organic light emitting layer that emits light by combining holes provided from the anode and electrons provided from the cathode is very vulnerable to moisture or oxygen, and thus a sealing structure is required.

On the other hand, in recent years, a flexible organic light-emitting display device that is manufactured to display an image even if it is bent like paper by forming a display area and wiring on a flexible substrate such as plastic, which is a flexible material, has been developed. It is attracting attention as a next-generation display device.

Flexible organic light-emitting display devices are being applied not only to computer monitors and TVs, but also to personal portable devices, and research on flexible organic light-emitting display devices having a large display area and reduced volume and weight is in progress. .

[Related technical literature]

1. Organic EL device and its manufacturing method (Korean Patent Application No. 10-2012-0157362)

The inventors of the present invention have been conducting research on a flexible organic light emitting display device that can be rolled up and stored like a scroll.

The flexible OLED display can be stored for a long time in the form of a scroll when stored. In addition, when the flexible OLED display is unfolded again, deformation may occur in the flexible OLED display due to storage for a long time.

The inventors of the present invention have studied elements that may cause deformation by analyzing organic relationships between various components of a flexible organic light emitting display device.

An object to be solved by the present invention is to provide a flexible organic light emitting display device in the form of a scroll having a structure capable of reducing deformation when stored for a long time.

In addition, another problem to be solved by the present invention is to provide a flexible organic light emitting display device in which the thickness of each substrate is adjusted so that the flexible organic light emitting display device can be rolled like a roll.

In addition, another problem to be solved by the present invention is configured to have a resilience that can not be deformed even if it is dried for a long time by adjusting the Young's-modulus value of the encapsulation portion of the flexible organic light emitting display device. It is to provide a flexible organic light-emitting display device that has high rigidity, that is, can not be damaged by a predetermined impact.

In addition, another problem to be solved by the present invention is to provide a flexible organic light emitting display device capable of improving the reliability and durability of an encapsulation portion of the flexible organic light emitting display device.

The problems of the present invention are not limited to the problems mentioned above, and other problems that are not mentioned will be clearly understood by those skilled in the art from the following description.

In order to solve the above-described problems, an organic light emitting display device according to an exemplary embodiment of the present invention is provided. The organic light emitting diode display includes a first flexible substrate, a second flexible substrate facing the first flexible substrate, a plurality of organic light emitting pixels disposed between the first flexible substrate and the second flexible substrate and disposed on the first flexible substrate, An adhesive layer disposed between the 1 flexible substrate and the second flexible substrate, an encapsulation unit configured to protect a plurality of organic light emitting pixels from oxygen and moisture, and an adhesive layer disposed on the encapsulation unit to bond the first flexible substrate and the second flexible substrate together. Includes. A neutral surface is formed adjacent to the plurality of organic light emitting pixels, and the elastic modulus value of the adhesive layer has a value equal to or greater than a predetermined elastic modulus so as not to be deformed by bending stress when the first flexible substrate is stored in a roll form, The thickness of the adhesive layer is determined in consideration of the thickness of the first flexible substrate, the critical radius of curvature of the first flexible substrate, and the elastic modulus of the adhesive layer.

According to another feature of the present invention, the first flexible substrate is configured to receive compressive stress, and the second flexible substrate is configured to receive tensile stress, so that when the first flexible substrate is rolled up, the first flexible substrate is applied to the first flexible substrate. It is configured to apply compressive stress and configured to apply tensile stress to the second flexible substrate.

According to another feature of the present invention, the second flexible substrate is made of a material having a relatively higher breaking strength against tensile stress than the first flexible substrate.

According to another feature of the present invention, the second flexible substrate is a metal substrate having a thickness of 10 μm to 120 μm.

According to another feature of the present invention, the first flexible substrate is made of a material having a relatively higher breaking strength against compressive stress than the second flexible substrate.

According to another feature of the present invention, the first flexible substrate is characterized in that it is a glass substrate etched to a thickness of 30 μm to 100 μm.

According to another feature of the present invention, the thickness of the adhesive layer is characterized in that 40㎛ 60㎛.

According to another feature of the present invention, the adhesive layer further includes a first adhesive layer disposed adjacent to the plurality of organic light emitting pixels and a second adhesive layer disposed adjacent to the second flexible substrate and containing a moisture absorbent.

According to another feature of the present invention, the thickness of the first adhesive layer is at least 5 μm or more and the thickness of the second adhesive layer is a thickness of the adhesive layer minus the thickness of the first adhesive layer.

According to another feature of the present invention, the adhesive layer is characterized in that it is an epoxy resin configured to have an elastic modulus of 900 MPa or more after curing.

According to another feature of the present invention, the first flexible substrate is configured to be rolled above a radius of curvature value capable of maintaining elastic deformation properties, and the second flexible substrate is configured to be rolled above a radius of curvature value capable of maintaining elastic deformation characteristics. It is configured, and the adhesive layer is configured to have pseudoelastic deformation characteristics, and each of the elastic modulus of the first flexible substrate and the second flexible substrate may be greater than the elastic modulus of the adhesive layer.

According to another feature of the present invention, the first flexible substrate is configured to have brittle properties while having elastic deformation properties, the first flexible substrate is configured to be rolled below the brittle stress value, and the second flexible substrate is elastic. The second flexible substrate may be configured to have a deformation characteristic while having a plastic deformation characteristic, and the second flexible substrate may be configured to be rolled to a value less than or equal to a plastic deformation generating stress value.

According to another feature of the present invention, the adhesive layer is an elastic body,

The elastic modulus of the adhesive layer may be 5 MPa to 100 MPa.

According to another feature of the present invention, one surface of the first flexible substrate is configured to be etched,

The etched surface may be a surface configured to receive tensile stress.

In order to solve the above-described problems, an organic light emitting display device according to another exemplary embodiment of the present invention is provided. The organic light emitting diode display includes a first flexible substrate, a second flexible substrate facing the first flexible substrate, a plurality of organic light emitting pixels disposed between the first flexible substrate and the second flexible substrate and disposed on the first flexible substrate, An adhesive layer disposed between the 1 flexible substrate and the second flexible substrate, an encapsulation unit configured to protect a plurality of organic light emitting pixels from oxygen and moisture, and an adhesive layer disposed on the encapsulation unit to bond the first flexible substrate and the second flexible substrate together. Includes.

A neutral surface is formed adjacent to the plurality of organic light emitting pixels, the first flexible substrate is configured to be rolled to a value of a radius of curvature that can maintain elastic deformation characteristics, and the second flexible substrate is configured to maintain elastic deformation characteristics. It is configured to be rolled to a value of a radius of curvature or more, the adhesive layer is configured to have pseudoelastic deformation properties, and the elastic modulus of the first flexible substrate and the elastic modulus of the second flexible substrate are greater than the elastic modulus of the adhesive layer.

Details of other embodiments are included in the detailed description and drawings.

According to the present invention, deformation when the flexible organic light emitting display device is rolled like a roll and stored for a long time can be minimized.

According to the present invention, a critical radius of curvature, which is a limit in which the flexible OLED display can be rolled, can be reduced by minimizing the thickness of the encapsulation portion of the flexible OLED display.

The effects according to the present invention are not limited by the contents exemplified above, and more various effects are included in the present specification.

1 is a schematic cross-sectional view illustrating a flexible organic light emitting display device according to an exemplary embodiment of the present invention.
2 is a graph illustrating a thickness relationship according to a critical radius of curvature of a first flexible substrate of a flexible OLED display according to an exemplary embodiment of the present invention.
3 is a schematic diagram for explaining a stress relaxation principle according to a thickness of a first flexible substrate and a thickness of an adhesive layer of a flexible OLED display according to an exemplary embodiment of the present invention.
4 is a cross-sectional view schematically illustrating a flexible organic light emitting display device according to another exemplary embodiment of the present invention.

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms. It is provided to completely inform the scope of the invention to the possessor, and the invention is only defined by the scope of the claims.

The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for explaining the embodiments of the present invention are exemplary, and thus the present invention is not limited to the illustrated matters. The same reference numerals refer to the same elements throughout the specification. In addition, in describing the present invention, when it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. When'include','have','consists of' and the like mentioned in the present specification are used, other parts may be added unless'only' is used. In the case of expressing the constituent elements in the singular, it includes the case of including the plural unless specifically stated otherwise.

In interpreting the constituent elements, it is interpreted as including an error range even if there is no explicit description.

In the case of a description of the positional relationship, for example, if the positional relationship of two parts is described as'upper','upper of','lower of','next to', etc.,'right' Or, unless'direct' is used, one or more other parts may be located between the two parts.

When an element or layer is referred to as “on” another element or layer, it includes all cases in which another layer or another element is interposed directly on or in the middle of another element.

Various physical property values such as modulus of elasticity, stress, pressure, viscosity, adhesion, and stiffness are interpreted as being described based on room temperature unless otherwise noted. Room temperature may mean, for example, a temperature of about 15°C to 35°C, more specifically about 20°C to 25°C, and more specifically about 25°C.

Unless otherwise specified, the adhesion is interpreted as being described based on the adhesion of the glass.

Although the first, second, etc. are used to describe various components, these components are not limited by these terms. These terms are only used to distinguish one component from another component. Accordingly, the first component mentioned below may be a second component within the technical idea of the present invention.

The same reference numerals refer to the same elements throughout the specification.

The size and thickness of each component shown in the drawings are illustrated for convenience of description, and the present invention is not necessarily limited to the size and thickness of the illustrated component.

Each of the features of the various embodiments of the present invention may be partially or entirely combined or combined with each other, and as a person skilled in the art can fully understand, technically various interlocking and driving are possible, and each of the embodiments may be independently implemented with respect to each other. It may be possible to do it together in a related relationship.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic cross-sectional view illustrating a flexible organic light emitting display device according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a flexible organic light emitting display device 100 according to an embodiment of the present invention includes a first flexible substrate 102, a plurality of organic light emitting pixels 104, an encapsulation part 106, and an adhesive layer 108. And a second flexible substrate 110.

The first flexible substrate 102 is configured to have flexible characteristics. A plurality of organic light emitting pixels 104 are disposed on the first flexible substrate 102 and configured to display an image through the plurality of organic light emitting pixels 104. An encapsulation part 106 is disposed on the plurality of organic light emitting pixels 104 to protect the plurality of organic light emitting pixels 104 from oxygen and moisture. The adhesive layer 108 is configured to bond the encapsulation part 106 of the first flexible substrate 102 and the second flexible substrate 110.

The flexible organic light emitting display device 100 is configured to be rolled in the form of a roll. Specifically, the first flexible substrate 102 and the second flexible substrate 110 of the flexible OLED display 100 are made of different materials. The flexible organic light emitting display device 100 is configured to be rolled in the direction of the first flexible substrate 102.

That is, when the first flexible substrate 102 is in the form of a roll, it is configured to receive compressive stress. In this case, the plurality of organic light emitting pixels 104 are configured to be positioned on a neutral plane (NP). The sealing portion 106 is configured to have a value equal to or greater than a predetermined elastic modulus so as not to be deformed by bending stress when stored in a roll form. The second flexible substrate 110 is configured to receive tensile stress when it is in the form of a roll. In addition, the second flexible substrate 110 is made of a material having a relatively higher breaking strength against tensile stress than the first flexible substrate 102.

2 is a graph illustrating a thickness relationship according to a critical radius of curvature of a first flexible substrate of a flexible OLED display according to an exemplary embodiment of the present invention.

Equation 1 is an equation describing a correlation between a critical radius of curvature and a thickness of a first flexible substrate of a flexible OLED display according to an exemplary embodiment of the present invention.

Hereinafter, a method of selecting the thickness of the first flexible substrate 102 so that the flexible organic light emitting display device 100 according to an embodiment of the present invention can be rolled like a scroll will be described with reference to FIGS. 1, 2 and Equation 1 .

The first flexible substrate 102 is configured to have flexible characteristics. The first flexible substrate 102 may be, for example, an organic or inorganic material, optically transparent, flexible, and excellent in chemical resistance, so that a high-temperature deposition process is possible. The first flexible substrate 102 may be, for example, a glass having excellent water vapor transmission rate (WVTR), flexible, and transparent to a visible light band. In order to have the above-described characteristics, the glass applied to the first flexible substrate 102 must have a thin thickness. However, since glass is fragile to impact, in order to roll like a roll while having sufficient rigidity according to an embodiment of the present invention, the thickness of the glass substrate must be determined in consideration of various factors.

For example, when the flexible OLED display 100 is rolled in a circular shape, the radius of a circle that the flexible OLED display 100 can roll to the smallest size may be determined as 100 mm. In this case, the curvature ratio R of the first flexible substrate 102 is 100R.

Alternatively, the radius of the circle can be determined as 50 mm. In this case, the curvature ratio R of the first flexible substrate 102 is 50R.

The thickness of the first flexible substrate 102 is determined based on a first critical bending stress threshold (σ _TH MPa) and a Young's modulus (E) value. In this case, the values of the first critical bending breakage point (σ _TH ) and the elastic modulus (E) may be constants of a material applied to the first flexible substrate 102.

For example, when the first flexible substrate 102 is made of glass, the first critical bending breakage point σ _{TH of} the first flexible substrate 102 may be 50 MPa. And the modulus of elasticity (E) may be 71.5 ㎬. In this case, if the radius of curvature R of the first flexible substrate 102 is 100R, the maximum thickness of the first flexible substrate 102 may be determined using the following equation.

[Equation 1]

In Equation 1, σ _TH means the first critical bending failure point. E means the modulus of elasticity. T means the thickness of the first flexible substrate 102. R _TH means the critical radius of curvature.

When, for example, the critical radius of curvature R _TH of the flexible OLED display 100 is determined to be 100R with reference to Equation 1. The first critical bending breakage point (σ _TH ) may be 50 MPa and the modulus of elasticity (E) may be 71.5 GPa. Therefore, the thickness (T) of the first flexible substrate 102 should be approximately 0.14 mm or less.

When, for example, the critical radius of curvature R _TH of the flexible OLED display 100 is determined to be 50R with reference to Equation 1. The first critical bending breakage point (σ _TH ) may be 50 MPa and the modulus of elasticity (E) may be 71.5 GPa. Therefore, the thickness (T) of the first flexible substrate 102 should be approximately 70 μm or less.

In summary, the thickness of the first flexible substrate 102 is proportional to _{the critical radius of curvature R TH of the flexible OLED display 100.}

For example, the first flexible substrate 102 may be a substrate etched to achieve a _{target critical radius of curvature R TH.} Specifically, during the process of forming the plurality of organic light emitting pixels 104 on the first flexible substrate 102, the thickness of the substrate should be 1 mm or more in order to maintain the flatness of the substrate. However, after the organic light emitting pixel 104 is formed, in _{order to reduce the critical radius of curvature R TH} , the thickness of the first flexible substrate 102 must be reduced. Therefore, the first flexible substrate 102 has an advantage in a process that can be etched after the organic light emitting pixel 104 is formed.

For example, the thickness of the first flexible substrate 102 may be 30 μm to 100 μm in consideration of the _{critical radius of curvature R TH.}

For example, the first flexible substrate 102 may be made of a material having a relatively higher breaking strength against compressive stress than the second flexible substrate 110.

That is, the first flexible substrate 102 is configured to have a first thickness that is not etched when the organic light emitting pixel 104 is formed, and after the organic light emitting pixel 104 is formed, an etched thinner than the first thickness is formed. It is configured to have 2 thickness. The plurality of organic light emitting pixels 104 are disposed on the first flexible substrate 102 having a thickness T determined in consideration of a predetermined _{critical radius of curvature R TH.} The plurality of organic light emitting pixels 104 include at least an organic light emitting diode (OLED) and a driving circuit. The organic light emitting diode includes at least an anode, an organic light emitting layer, and a cathode. A bank may be disposed between each organic light emitting pixel arranged to distinguish each organic light emitting pixel. The anode may be patterned to correspond to each of the organic light emitting pixels, and the outside of the anode may be configured to cover the bank. The organic light emitting diode may be configured in various ways, and may be configured to include, for example, an electron transport layer (ETL), an emission layer (EML), a hole transport layer (HTL), and the like. It is also possible that a capping layer is further disposed on the cathode. The driving circuit unit includes a switching transistor, a driving transistor, and a capacitor. Each transistor may include a gate electrode formed of a gate line, a source electrode and a drain electrode formed of a data line, and may be configured to adjust the amount of current of the driving transistor in proportion to the data voltage applied to the driving transistor. The driving transistor is connected to the anode of the organic light emitting diode to supply current.

The plurality of organic light emitting pixels 104 may have a thickness of 1 μm to 10 μm, for example. The thickness may include the above-described wirings of the driving circuit unit, the stacking thickness of the passivation layer and the planarization layers insulating each of the wirings, and the height of the organic light emitting diode and the bank.

The neutral surface NP of the flexible organic light emitting display device 100 is configured to be adjacent to the surface on which the plurality of organic light emitting pixels 104 are formed. The neutral surface NP is, for example, when the flexible OLED display 100 is bent, tensile stress is generated on one side of the flexible organic light emitting display device 100 as a boundary, and compressive stress is generated on the other side. ) Occurs. So, in the middle, there is a surface without stretching, and this surface is defined as a neutral surface (NP). In theory, bending stress does not occur at the neutral plane NP.

When the neutral plane NP is formed at the position where the plurality of organic light emitting pixels 104 are disposed, since stress is not generated in the plurality of organic light emitting pixels 104 when the flexible organic light emitting display device 100 is bent, a plurality of There is an advantage of minimizing damage to the organic light emitting pixel 104 of. However, the present invention is not limited thereto, and the neutral surface NP may be configured to be positioned at an interface between the organic light emitting pixel 104 and the adhesive layer 108. In this case, since stress is not generated at the interface between the organic light emitting pixel 104 and the adhesive layer 108, delamination may not occur at each interface. To further explain, the position of the neutral plane NP may be configured to be located within ±15 μm from the plurality of organic light emitting pixels 104. However, it is not limited thereto. If the position of the neutral plane NP is significantly separated from the organic light emitting pixel 104, since stress may be applied to the organic light emitting pixel 104 to generate stress in the organic light emitting pixel 104, the neutral plane ( NP) should be configured to be disposed around the organic light emitting pixel 104.

The encapsulation part 106 may be formed of an inorganic material, and may be formed of, for example, silicon nitride (SiN _x ), silicon oxide (SiO _x ), or aluminum oxide (Al ₂ O ₃ ), and moisture permeability ( It is preferable to select a material with excellent WVTR).

The sealing portion 106 is configured to be disposed adjacent to the neutral surface NP. According to the above-described configuration, since the bending stress applied to the encapsulation part 106 can be reduced, the possibility of occurrence of cracks or damage in the inorganic material layer constituting the encapsulation part 106 is significantly reduced. Accordingly, durability against bending of the flexible organic light emitting display device 100 may be improved.

The encapsulation part 106 may be formed in a single inorganic film structure. However, the present invention is not limited thereto, and the encapsulation part 106 forms a first inorganic film and then arranges an overcoat layer capable of compensating for foreign substances thereon, and the second inorganic film disposed on the overcoat layer is sealed with the first inorganic film, thereby causing a foreign substance defect. It can be applied in a structure that can compensate for.

The adhesive layer 108 is disposed on the encapsulation part 106. The adhesive layer 108 is configured to fix the first flexible substrate 102 and the second flexible substrate 110.

The adhesive layer 108 fixes the first flexible substrate 102 and the second flexible substrate 110 with a predetermined adhesive force, and at the same time, it is dried and stored for a long time in a rolled state having a predetermined radius of curvature, and then flattened again. It is configured with a predetermined thickness so as to have a restoring force and at the same time secure stiffness that can not be damaged against external impacts.

First, the adhesive layer 108 is configured to have a predetermined adhesive force. The adhesive layer 108 is configured to increase adhesive strength through a curing process. After curing, the adhesive strength of the adhesive layer 108 is configured to be at least 450 gf/10 mm or more. If the adhesion is too low, there may be a problem in that the first flexible substrate 102 and the second flexible substrate 110 may be peeled off from each other. Therefore, when the adhesive layer 108 is rolled, it is configured to have sufficient adhesive force to the extent that peeling does not occur on the adhesive surface.

Second, the adhesive layer 108 is configured to have a predetermined modulus of elasticity (E). In addition, the elastic modulus of the adhesive layer 108 is configured to be smaller than the elastic modulus of the first flexible substrate 102. When the elastic modulus of the adhesive layer 108 is less than the elastic modulus of the first flexible substrate 102, the adhesive layer 108 has an advantage of absorbing stress applied to the first flexible substrate 102.

For example, the elastic modulus (E) after curing of the adhesive layer 108 may be 900 MPa or more. For example, if the modulus of elasticity (E) is too low, a problem in that the flexible OLED display may be easily deformed may occur. In other words, when the elastic modulus (E) is low, the flexible organic light emitting display device is easily deformed, and when stored in a roll form for a long time, the adhesive layer 108 absorbs the bending stress, causing a problem that may be deformed into a bent state. I can. In particular, such a problem can be fatal in a flexible organic light emitting display device in the form of a scroll.

For example, when the elastic modulus (E) after curing of the adhesive layer is as low as 800 MPa, since the adhesive layer 108 can absorb stress well, there is an advantage in terms of bending properties. However, when stored in the form of a roll for a long time, there is a problem in that the shape of the adhesive layer 108 may be deformed by the stress applied for a long time. Accordingly, it is difficult to apply an adhesive layer having an elastic modulus (E) of 800 MPa or less to a roll-type flexible organic light-emitting display device.

Third, the adhesive layer 108 is configured to have a predetermined thickness. For example, when the first flexible substrate 102 is glass, it has a property of being easily broken by external impact. Specifically, when the first flexible substrate 102 is etched glass, it becomes more susceptible to external impact. In addition, when cracks and damages occur in the first flexible substrate 102, moisture and oxygen may penetrate into the organic light emitting pixel 106, and thus defects may occur.

However, when the first flexible substrate 102 is made of glass, it may have a surface flaw, a scratch, or a surface damage generated during a manufacturing process. And when the glass substrate is bent, the tensile stress is concentrated on surface defects or scratches or surface damage. Thus, breakage occurs from defects, scratches or surface damage. However, through the etching process, there is an advantage in that such surface defects, scratches, or damage can be removed. Therefore, even if the thickness of the flexible substrate 102 is substantially reduced, there is an advantage in that the reliability against tensile stress can be increased.

3 is a schematic diagram illustrating a stress relaxation principle according to a thickness of a first flexible substrate and a thickness of an adhesive layer of a flexible OLED display according to an exemplary embodiment of the present invention.

Equation 2 is an equation describing stress according to the thickness of the first flexible substrate and the thickness of the adhesive layer of the flexible organic light emitting display device according to the exemplary embodiment of FIG. 3.

Hereinafter, a method of selecting the thickness of the adhesive layer 108 of the flexible organic light emitting display device 100 according to an exemplary embodiment will be described with reference to FIGS. 3 and 2.

The adhesive layer 108 is configured to increase the rigidity of the first flexible substrate 102 against external impact. A method of measuring stiffness, for example, is the ball drop test. The ball drop test is a method of measuring damage to the flexible organic light emitting display device 100 by free-falling an iron ball having a predetermined diameter at a predetermined height, and the critical radius of curvature (R _TH ) of the first flexible substrate 102 Is correlated with. That is, as the thickness of the first flexible substrate 102 decreases in order to reduce the critical radius of curvature R _TH , the rigidity of the flexible organic light emitting display device 100 may be weakened in inverse proportion to this.

[Equation 2]

In Equation 2, U _T denotes a total energy value generated when a metal ball having a predetermined diameter freely falls and collides with the flexible OLED display 100. E _g denotes the elastic modulus (E) of the first flexible substrate 102. h _g means the thickness of the first flexible substrate 102. R denotes a degree of a deformed radius of curvature of the first flexible substrate 102 in which the first flexible substrate 102 is deformed by an external impact. E _p means the elastic modulus (E) of the adhesive layer 108. h _p means the thickness of the adhesive layer 108. In FIGS. 3 and 2, a denotes a radius of the region of the first flexible substrate 102 that has been deformed. In FIG. 3 and Equation 2, d denotes the depth of a mark in which the first flexible OLED display 100 enters the adhesive layer 108 due to free fall of the iron beads. According to Equation 2, the total energy U _T is configured to be dispersed while the first flexible substrate 102 and the adhesive layer 108 are deformed. At this time, when the U _T value becomes more than a threshold value that the first flexible substrate 102 can handle, it is destroyed.

Using Equation 2, it was found that damage to the first flexible substrate 102 can be prevented by reducing the elastic modulus (E _p ) of the adhesive layer 108 or by reducing the thickness (h _{p) of the adhesive layer 108.} I can. As described above, if the elastic modulus (E _p ) of the adhesive layer 108 decreases, a problem of deformation when the flexible organic light emitting display device 100 is stored in a roll for a long time may occur. Therefore, the elasticity of the adhesive layer 108 The modulus is configured to be equal to or greater than a predetermined modulus of elasticity. For example, the elastic modulus (E _p ) of the adhesive layer 108 is configured to be 900 MPa or more.

The thickness of the adhesive layer 108 is configured to increase in correspondence with the _{modulus of elasticity (E p ).} For example, the thickness of the adhesive layer 108 is configured to be at least 40 μm or more. However, when the thickness of the adhesive layer 108 becomes thicker than a certain amount, the thickness of the flexible organic light emitting display device 100 also increases. Therefore, the thickness is configured to be less than 60㎛.

Referring back to FIG. 1, the second flexible substrate 110 is configured to have flexible characteristics. The second flexible substrate 110 is made of a material having a relatively higher breaking strength than the first flexible substrate 102. For example, the second flexible substrate 110 may be a metal plate. The second flexible substrate 110 may be formed in the form of a metal plate or foil made of copper or aluminum.

In particular, when the flexible OLED display 100 is configured to be rolled in the direction of the first flexible substrate 102, the second flexible substrate 110 is always configured to receive a tensile stress.

If the first flexible substrate 102 and the second flexible substrate 110 are made of the same material, the first flexible substrate 102 is configured to receive compressive stress and the second flexible substrate 110 receives tensile stress. It is composed. However, glass is not easily damaged by compressive stress, but is easily damaged by tensile stress. Accordingly, when the second flexible substrate 110 is made of glass or rolled in a rolled state, the second flexible substrate 110 may be damaged.

If the second flexible substrate 110 is a metal plate made of copper or aluminum, the above-described materials are not easily damaged by tensile stress. Therefore, when the flexible organic light emitting display device 100 according to the exemplary embodiment of the present invention is configured to be rolled in the direction of the first flexible substrate 102, the first flexible substrate 102 and the second flexible substrate 110 are subjected to stress. It has the advantage of not being damaged by.

For example, the thickness of the second flexible substrate 110 may be determined within 10 μm to 120 μm.

4 is a cross-sectional view schematically illustrating a flexible organic light emitting display device according to another exemplary embodiment of the present invention.

Hereinafter, for convenience of description, a portion of the flexible organic light emitting display device 200 according to another embodiment of the present invention that is differentiated from that of the flexible organic light emitting display device 100 according to an embodiment of the present invention will be described. A description overlapping with that of the flexible organic light emitting display device 100 will be omitted.

Referring to FIG. 4, the adhesive layer 208 of the flexible OLED display 200 includes at least two layers. The first adhesive layer 218 of the adhesive layer 208 is configured to be disposed in the direction of the first flexible substrate 202. The second adhesive layer 228 is configured to be disposed in the direction of the second flexible substrate 210. The second adhesive layer 228 is configured to include a desiccant 238. The adhesive layer according to the embodiments of the present invention may be formed to be relatively thicker than conventional adhesive layers in consideration of the bending characteristics and rigidity of the first flexible substrate. In addition, since the adhesive layer 208 has a relatively insufficient effect of preventing moisture permeation than that of the second flexible substrate 210, the adhesive layer 208 may be a side moisture permeable path. Particularly, as the thickness of the adhesive layer 208 increases, a side moisture permeation problem may occur, so that the second adhesive layer 228 is configured to include a moisture absorbent 238. In addition, since the desiccant 238 may damage the sealing portion 206, the first adhesive layer 218 is configured to have a predetermined distance to protect the sealing portion 206 from the desiccant 238. Further, a plurality of organic light emitting pixels 204 are disposed on the first flexible substrate 202.

For example, the first adhesive layer 218 may be configured to have a thickness of 5 μm to 8 μm in order to protect the encapsulation portion 206 from the desiccant 238 of the second adhesive layer 228. In the second adhesive layer 228, the sum of the thickness of the first adhesive layer 218 and the thickness of the second adhesive layer 228 is at least 40 μm to 60 μm in order to delay the rigidity and side penetration of the first flexible substrate 202. It can be configured to be. However, it is not limited thereto.

In some embodiments, the flexible OLED display may be configured to be disposed in a rollable device.

In some embodiments, one side of the flexible OLED display may be fixed to a cylinder having a predetermined diameter, and may be configured to be wound or unfolded by rotation of the cylinder.

Embodiments of the present invention can be summarized once again as follows:

In the flexible organic light emitting display device according to the exemplary embodiments, a first flexible substrate having a plurality of organic light emitting pixels disposed thereon, a second flexible substrate disposed so as to face a plurality of organic light emitting pixels of the first flexible substrate, and a first flexible light emitting display device It includes an adhesive layer bonding the substrate and the second flexible substrate, and when the flexible organic light emitting display device is rolled in the direction of the first flexible substrate, a neutral surface that does not generate stress due to bending is formed adjacent to the plurality of organic light emitting pixels. It is configured to protect the light-emitting pixel from stress.

The first flexible substrate of the flexible OLED display according to the exemplary embodiments of the present invention is made of a material having a high elastic modulus in order to become flat when unfolded in a rolled state. For example, the first flexible substrate is made of etched glass. According to the above configuration, when the organic light emitting pixel is formed, it has the advantage of maintaining the flatness of the substrate to satisfy the yield and processing conditions. After the organic light emitting pixel is formed, it is etched to a preset thickness, so that the target flexible organic light emitting display It has the advantage of being able to achieve the target critical radius of curvature of the device.

The adhesive layer of the flexible OLED display according to the exemplary embodiments of the present invention is made of a material having a predetermined elastic modulus value or more so as not to be deformed in a rolled state. In addition, in order to relieve the compressive stress of the first flexible substrate, it is configured to have an elastic modulus that is relatively smaller than that of the first flexible substrate. That is, the elastic modulus value of the adhesive layer is smaller than the elastic modulus value of the first flexible substrate and is configured to be equal to or greater than a predetermined elastic modulus value so that the flexible OLED display does not deform when stored in a scroll form for a long time.

The adhesive layer of the flexible OLED display according to the exemplary embodiments of the present invention is configured to have a thickness determined in consideration of the thickness of the first flexible substrate and the rigidity of the flexible OLED display. That is, the adhesive layer is configured to have a predetermined thickness or more in order to achieve the desired rigidity of the flexible organic light emitting display device. In addition, the adhesive layer is configured to be less than or equal to a predetermined thickness in consideration of the critical radius of curvature of the flexible OLED display. That is, the thickness of the adhesive layer is configured to be determined within a range in which a critical radius of curvature of the flexible organic light emitting display device may not increase while having a desired stiffness in the thickness of the first flexible substrate.

The second flexible substrate of the flexible OLED display according to the exemplary embodiments of the present invention is made of a material having a high modulus of elasticity in order to become flat when unfolded in a rolled state. In addition, since the second flexible substrate is configured to generate tensile stress when it is rolled, the second flexible substrate is configured such that a material having relatively better durability against tensile stress than the first flexible substrate is applied. For example, the first flexible substrate is made of a metallic material. According to the above-described configuration, when the flexible OLED display is rolled into a roll, damage due to tensile stress can be prevented.

In some embodiments, the flexible OLED display may be configured to be rolled to a radius of curvature that can maintain elastic deformation.

Specifically, the first flexible substrate is configured to be rolled over a radius of curvature capable of maintaining elastic deformation. In addition, the second flexible substrate is configured to be rolled over a radius of curvature capable of maintaining elastic deformation. "Elastic deformation" as used herein refers to a characteristic in which deformation is restored as soon as stress is removed, even if stored in a dried state for a long time.

In addition, the adhesive layer between the first flexible substrate and the second flexible substrate is configured to have an anelastic deformation characteristic. "Pseudoelastic deformation" as used herein refers to a property that, when stored in a dried state for a long time, does not recover, or recovers after a certain period of time, even if stress is removed.

In addition, the elastic modulus of the first flexible substrate and the second flexible substrate are configured to be greater than the elastic modulus of the adhesive layer. For example, the first flexible substrate and/or the second flexible substrate may be made of one of glass, metal, and ceramic. In addition, the adhesive layer may be made of a polymer.

According to the above-described configuration, even if the flexible organic light emitting display device is stored in a curled state for a long time, the first flexible substrate and the second flexible substrate are rolled over a radius of curvature capable of maintaining elastic deformation, so that elastic properties can be maintained. However, since the adhesive layer has pseudoelastic deformation properties, deformation may occur when stored in a dried state for a long time. However, since the elastic modulus of the first and second flexible substrates is greater than that of the adhesive layer, the adhesive layer can be restored flat by the first and second flexible substrates.

In some embodiments, the flexible organic light emitting display device may be configured to maintain elastic deformation characteristics while having brittle characteristics and plastic deformation characteristics.

Specifically, the first flexible substrate has elastic deformation characteristics and is configured to have brittle characteristics when a stress of more than a specific value is applied, and the second flexible substrate has elastic deformation characteristics and a stress of more than a specific value is applied. It is configured to have plastic deformation characteristics when it is formed. As used herein, "brittleness" refers to a property that is destroyed with little plastic deformation when deformed by stress.

The first flexible substrate is configured to be rolled to a value of brittleness generating stress or less. In addition, the second flexible substrate is configured to be rolled below a stress value of causing plastic deformation.

For example, the first flexible substrate may be made of glass. In addition, the second flexible substrate may be made of metal.

According to the above-described configuration, even if the flexible OLED display is stored in a curled state for a long time, the first flexible substrate and the second flexible substrate are rolled over a radius of curvature capable of maintaining elastic deformation, and thus elastic properties can be maintained.

In particular, when the first flexible substrate has brittle properties, since it has excellent resilience, there is an advantage in that the flexible OLED display may not be deformed even if it is stored in a dried state for a long time.

In some embodiments, the adhesive layer may be composed of an elastomer. “Elastic body” as used herein refers to an elastic deformation such as rubber (for example, a very large deformation capable of recovering at a low stress level). _{For example, the elastic modulus (E p} ) of the adhesive layer, which is an elastic body, may be 5 MPa to 100 MPa. That is, the elastic body is easily deformed even under slight stress, and has a very good resilience. Therefore, when the adhesive layer is an elastic body, since the elastic modulus value is very small, there is an advantage in that the deformation of the flexible organic light emitting display device may not be affected.

In some embodiments, at least one surface of the first flexible substrate may be etched. For example, by etching the first surface of the first flexible substrate, surface defects, scratches, or surface damages formed on the first surface may be removed. In particular, the etched surface may be a surface when tensile stress is applied. According to the above-described configuration, even if only one surface of the first flexible substrate is etched, there is an advantage of improving the reliability of the flexible organic light emitting display device.

In some embodiments, both surfaces of the first flexible substrate may be etched. For example, by etching the first and second surfaces of the first flexible substrate, surface defects, scratches, or surface damages formed on the first and second surfaces may be removed. According to the above-described configuration, there is an advantage in that both sides of the first flexible substrate can be etched to shape the reliability of the flexible organic light emitting display device.

Although the embodiments of the present invention have been described in more detail with reference to the accompanying drawings, the present invention is not necessarily limited to these embodiments, and various modifications may be made without departing from the spirit of the present invention. . Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain the technical idea, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

100, 200: flexible organic light emitting display device
102: first flexible substrate
104: organic light emitting pixel
106: bag
108, 208: adhesive layer
218: first adhesive layer
228: second adhesive layer
238: desiccant
110: second flexible substrate

Claims (20)

In the flexible organic light emitting display device,
A first flexible substrate;
A second flexible substrate disposed to face the first flexible substrate;
A plurality of organic light emitting pixels disposed between the first flexible substrate and the second flexible substrate and disposed on the first flexible substrate; And
Including an adhesive layer configured to adhere the first flexible substrate to the second flexible substrate,
In the flexible OLED display, when the first and second flexible substrates are bent in the direction of the first flexible substrate,
The second flexible substrate is composed of a metal plate having a higher breaking strength against tensile stress than the first flexible substrate,
A flexible organic light-emitting display device, wherein an elastic modulus of the first flexible substrate and an elastic modulus of the second flexible substrate are greater than that of the adhesive layer so that the second flexible substrate can be flattened. The method of claim 1,
When the flexible OLED display is rolled, the first flexible substrate is configured to receive a compressive stress, and the second flexible substrate is configured to receive a tensile stress. The method of claim 1,
The second flexible substrate has a thickness of between 10 μm and 120 μm. The method of claim 1,
The flexible organic light emitting display device, wherein the first flexible substrate includes a glass substrate. The method of claim 1,
The first flexible substrate has a thickness between 30 µm and 100 µm. The method of claim 1,
The adhesive layer has a thickness of between 40 μm and 60 μm. The method of claim 1, wherein the adhesive layer,
A first adhesive layer adjacent to the plurality of organic light emitting pixels; And
Including a second adhesive layer on the second flexible substrate,
The second adhesive layer is configured to include a desiccant. The method of claim 7,
The first adhesive layer has a thickness of at least 5 μm. The method of claim 7,
The thickness of the second adhesive layer is equal to a thickness of the adhesive layer minus the thickness of the first adhesive layer. The method of claim 1,
The first flexible substrate and the second flexible substrate have elastic deformation characteristics that return to a flat shape as soon as the stress is removed after the flexible OLED display is rolled to a radius of curvature equal to or greater than a minimum radius of curvature,
The adhesive layer has an inelastic deformation characteristic. The method of claim 1,
The adhesive layer has an elastic modulus of 900 MPa or more in a bent state to reduce a degree of deformation when the flexible OLED display is stored in the form of a roll. The method of claim 1,
When the flexible organic light emitting display device is rolled in the direction of the first flexible substrate, a neutral surface is provided adjacent to the plurality of organic light emitting pixels to prevent bending stress due to bending to protect the plurality of organic light emitting pixels from the stress. The flexible organic light emitting display device. The method of claim 1,
The flexible organic light emitting display device is configured to be stored in the form of the scroll for at least 100 hours. The method of claim 1,
Further comprising an encapsulation portion between the plurality of organic light emitting pixels and the second flexible substrate,
The flexible organic light emitting display device, wherein the encapsulation part is configured to protect the plurality of organic light emitting pixels from oxygen and moisture. In a rollable display device,
A first substrate having a first elastic modulus value;
A plurality of sub-pixels on the first substrate;
An adhesive layer disposed on the plurality of sub-pixels and having a second elastic modulus value; And
And a second substrate disposed on the adhesive layer and having a third elastic modulus value different from the first elastic modulus value,
The first substrate is configured such that compressive stress is applied when the rollable display device is rolled,
The second substrate is configured to apply a tensile stress when the rollable display device is rolled,
The first elastic modulus value is greater than the second elastic modulus value,
The third elastic modulus value is greater than the second elastic modulus value. The method of claim 15,
The first substrate includes an organic material or an inorganic material. The method of claim 16,
The first substrate is optically transparent, has flexible characteristics, and has chemical resistance. The method of claim 15,
The second substrate has a tensile stress greater than that of the first substrate. The method of claim 15,
The rollable display device, wherein the adhesive layer has an adhesive force capable of preventing peeling of the first substrate and the second substrate when the rollable display device is rolled. The method of claim 19,
The adhesive force is 450 gf / 10 mm or more, the display device that can be rolled.

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